Question

500 J of work are done on a system in a process that decreases the system’s thermal energy by 200 J. How much heat energy is transferred to or from the system?

Short answer

The value of heat is -700J

Step-by-step solution

Definition of first law of thermodynamics

First law of thermodynamics define the energy does not create or destroy in the universe.

Finding the value of heat energy 

As $E_{thi}=W+Q$

The work done is positive as energy is transferred from environment to gas.

$\begin{array}{rcl}{E}_{thi}& =& -200J\\ W& =& +500J\end{array}$

Now applying all values

The value of heat is $\begin{array}{rcl}{E}_{thi}& =& -200J\\ W& =& +500J\\ Q& =& E_{thi=}-W\\ & =& -200J-500J\\ & =& -700J\end{array}$